Inchworm not powering up

[Hedos]

Hello!

I just finished building my Inchworm, after applying power to the board, the LED didn't light up.. So I started investingating what might be the problem.

Do you have suggestions to help me troubleshoot? Any idea what is most susceptible to have gone wrong? Any other thing I should examine?

Here's the summary of what I found:

I'm using a adjustable 3~12VDC@800mA adapter to power the board. I set it to output 9 volts (it seems to always output a higher voltage at low current intensity though, so it should be normal to read about 12 volts if the current is low)

The voltage between GND and the positive side of the power jack is read by my multimeter as 12.20 volts. The voltage between the GND and past the first component, the power diode D1, is only 60 mV. After that is the LM7805 regulator. The voltage between ground and the middle or right pin of the LM7805 is 0V. (The left pin is connected to D1, so the voltage is of course 60 mV there too). The voltage between any other point on the board, such as the +5V reference, and the ground, is 0V.

I tested the diodes, they all appear fine (Block reverse current and otherwise allow current for >0.5V)

I read a resistance of 3.25 kohms between the +5V and GND references.

The LED indicating the board is powered has been tested and works fine.

All the solder joints seem good too.

It might be good to note, though, that I may have heated a lot (too much) some stuff. This was my first experience with soldering and before I got used to it, it took me a lot of heating to succeed with some joints. I was more careful with the sensible components though, such as diodes and transistors. Also, sometimes the part of the PCB around the joints seem to have melted a bit... it looks a bit like wax at some point. Maybe have I destroyed an electrical link printed on the PCB, is that possible? Maybe I have created a short circuit too... Nothing seem to suggest that in my previous analysis, though.

Thanks a lot for helping.

 

[Hedos]

One more thing... the voltage regulator (LM7805) is full of some kind of white dust... is this normal? Maybe does it prohibit electrical contact?
I've seen other regulators or chips with white stuff on it too.. what is it exactly?

Anyway, the region with the regulator and the diode D1 do seem suspicious with the 60mV...
Why is there a need for a diode in this circuit anyway? What is its purpose? Should I try shorting out the diode and see if the power LED lights up or is that dangerous?

 

[Hedos]

Huh... forget it guys, I found the problem. It looks like that stupid universal adapter was outputting current in the wrong direction. (The interior of the plug was negative instead of positing)

The board works fine.. and that explains the diode thing.

 

[mramos1]

Check GND to the input on the regulator, make sure you have the 12VDC there. Cathode side of D1/D2. D2 is a protection diode, so the +12 should go thru it and be on the input of the 7805 (pin1/VIN/left pin).

 

[mramos1]

My thought is the diode D2 is doing its job

 

[Hedos]

Yep, fortunatly I suppose

By the way, what is that white stuff on the regulator and some other chips pins?

 

[mramos1]

Yep, fortunatly I suppose

By the way, what is that white stuff on the regulator and some other chips pins?

Corrosion maybe? I do not have them on mine? Might want to clean it off though. Was it that way in the kits from blueroom or these your own parts. Also, could be tape from a reel. Use some cleaner of them, should be fine. All the heat from the iron and solder will do the rest.

I have parts that are 20+ years old and there is not white stuff on them. And they work fine.


EDIT: And yes, good thing Bill dropped D2 in there huh? And the .7V drop will save a little heat on the regulator as well.

 

[Hedos]

It is from the blueroom kit. Also, the 16F877 for the Inchworm has its pins covered with the same white stuff. The other chip, the 232, doesn't have anything on its pins though.

It easily is removed with a sharp/hard object, not just my fingers though, looks like some kind of dust.

 

[mramos1]

Did you get one of the other boards as well or just the inchworm?

I put an ICD2 set of pins on everything now. I have a couple proto boards (8pin and an 8/16 pin). If you want I can send you the eagle drawings and you can use the 8 pin to test it. Or you can build it on a proto board of some type.

The firefly is pretty nice to start with as well.

 

[mramos1]

It is from the blueroom kit. Also, the 16F877 for the Inchworm has its pins covered with the same white stuff. The other chip, the 232, doesn't have anything on its pins though.

It easily is removed with a sharp/hard object, not just my fingers though, looks like some kind of dust.

Sure it is fine. Tinning maybe on them. The pins should not look like chrome Long as solder sticks to them. Also, if not using sockets, do not overheat them.

EDIT: Nice place to start also is

 

[Hedos]

Sure it is fine. Tinning maybe on them. The pins should not look like chrome Long as solder sticks to them. Also, if not using sockets, do not overheat them.

Ok, good to know.

Did you get one of the other boards as well or just the inchworm?

I put an ICD2 set of pins on everything now. I have a couple proto boards (8pin and an 8/16 pin). If you want I can send you the eagle drawings and you can use the 8 pin to test it. Or you can build it on a proto board of some type.

The firefly is pretty nice to start with as well.

I only got the inchworm. I thought the Firefly wasn't out yet?
What is that eagle drawings?
Also, I'm not sure I get the full scope of the firefly. I suppose it allows you to program any chip on the ZIF sockets via the ICD cable connected to an Inchworm. What is supposed to be a PIC tutor? Why does it need to be so complex too?
I thought most of the job would be done by the programmer. I'd just like to simply get my chip actually programmed
Or I must be missing something.

edit:

EDIT: Nice place to start also is

I was looking through, that, seems interesting.

Does PGD and PGC stand for Program data and Program Clock, or something along those lines? That would fit with the schematics provided on that web site.

 

[eng1]

By the way, what is that white stuff on the regulator and some other chips pins?

It is oxide that forms naturally when metals are exposed to air.

 

[Hedos]

It is oxide that forms naturally when metals are exposed to air.

Ok, thanks. Could a large amount of oxidation obstruct electrical contact?

 

[mramos1]

Hedos:

Yea, the firefly I think is for intermediate users. If you wire the 3 LEDs to ground, it will make it a little simpler. I am getting my son into PICS and that was the first thing I saw was he needs to learn to send a high to an LED and ground a switch to start. Yes, the firefly will program chips as well, but it is really a training board.

Eagle is a program to make schematics and circuit boards. The 8 pin board (I mentioned) I made for proto types. You can solder in an LED/resistor and a switch/resistor and play. But if you have to ask what Eagle is, best thing is get a breadboard and hook the inchworm to the thing and go...

Then you move to the firefly. It allows you to learn to work with ADC, where you can read IR and pots. And has serial where you can talk to your PC serial port and much more.

 

[eng1]

Ok, thanks. Could a large amount of oxidation obstruct electrical contact?

It is removed and carried away when soldering.

 

[Hedos]

Eagle is a program to make schematics and circuit boards. The 8 pin board (I mentioned) I made for proto types. You can solder in an LED/resistor and a switch/resistor and play. But if you have to ask what Eagle is, best thing is get a breadboard and hook the inchworm to the thing and go...

Ok, well, do you have an eagle schematic that would show how to hook up a 16 pins PIC (16F628A) with the ICD2 cable so it can be programmed?

The firefly doesn't seem to be an option just right now.

 

[Hedos]

It is removed and carried away when soldering.

Not when you put a chip into a socket though.

 

[eng1]

Is it so strong? Don't worry and start programming!

 

[Hedos]

One more thing.. can't seem to find anywhere this "inchworm i type" connector for the cable provided in the kit.. They only provided one connector.

Where could I get such a connector to put on the other end?

 

[William At MyBlueRoom]

It is from the blueroom kit. Also, the 16F877 for the Inchworm has its pins covered with the same white stuff. The other chip, the 232, doesn't have anything on its pins though.

It easily is removed with a sharp/hard object, not just my fingers though, looks like some kind of dust.

If you bought the kit from DIPMicro he uses parts he supplies in the kit. I'm working on packaging and may sell the kits directly in the future. It's impossible to control quality otherwise.

Yep glad I added that diode. I've modded an inchworm for battery power and another for a hardwired 5V 2A switchmode wall adapter ($1.99 Sayal Canada) You don't need the 7805 in that mode.
**broken link removed**